This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Objective: To generate strong cytotoxic T lymphocytes (CTL) responses, in the absence of other immune responses, using several different vaccine approaches. All HIV vaccine efficacy trials to date have ended in failure. Structural features of the Env glycoprotein and its enormous variability have frustrated efforts to induce broadly-reactive neutralizing antibodies. To explore the extent to which vaccine-induced cellular immune responses, in the absence of neutralizing antibodies, can control replication of a heterologous, mucosal viral challenge, in 2007, we vaccinated eight macaques with a DNA/Ad5 regimen expressing all of the proteins of SIVmac239 except Env. Vaccinees mounted high-frequency T cell responses against 11-34 epitopes. In June 2008, we began to challenge the vaccinees and eight na[unreadable]ve animals with the heterologous biological isolate SIVsmE660, using a regimen intended to mimic typical human HIV exposures resulting in infection. Viral loads in the vaccinees were significantly less at both peak (1.9 log reduction p0.03) and at set point (3.3 log reduction p0.003) than those of control na[unreadable]ve animals. Five of eight vaccinated macaques controlled acute peak viral replication to less than 80,000 vRNA copy Eq/ml and to less than 100 vRNA copy Eq/ml in the chronic phase. Our results demonstrate that broad vaccine-induced cellular immune responses can effectively control replication of a pathogenic, heterologous AIDS virus, suggesting that T cell based vaccines may have greater potential than previously appreciated. We have a manuscript in submission at the Journal of Experimental Medicine. This research uses WNPRC Immunology and Virology Services, WNPRC Genetics Services (MHC typing).